1. Field of the Invention
The present invention relates to a display device, more precisely to a display device that contains two types of particles inside it.
2. Description of the Related Art
Heretofore known is an electronic paper technology of using electronic energy to display desired images on display devices. The electronic paper technology is essentially based on electrophoresis, thermal rewritability, liquid crystal conversion and electrochromism, and this is broadly divided into two categories. One is to use a display device in which a liquid display element or a liquid containing solid display element particles dispersed therein is sealed between a pair of substrates; and the other is to use a display device in which electroconductive particles of different colors serving as a display element and insulating particles are sealed between a pair of substrates each having an electrode and a dielectric layer laminated in that order on a support. Of the two, the latter display device is driven by an electric field applied between the substrates, in which one of the electroconductive particles and the triboelectrically-charged particles move to one of the pair of substrates while the other particles move to the other substrate to thereby form an image owing to the color contrast between the two types of the particles. The image thus formed is still kept as it is even after the electric field applied between the substrates is turned off. By switching the electric field applied, the image formation in the device is repeated.
In the display device of the type that contains two types of particles, the particles are triboelectrically charged to form an image. In this, however, the chargeability of the particles and the adhesiveness thereof to the substrates vary, depending on the change of the ambient humidity. Therefore, the display device could not all the time produce stable images. In addition, the electrodes formed on the substrates are deteriorated by moisture.
The present invention has been made in view of the above circumstances, and provides a display device containing two types of particles and capable of producing stable images.
The display device provided by the invention includes a pair of substrates which face each other and at least one of which transmits light, a spacer sandwiched between the pair of substrates, and two types of particles of different colors and different electric characteristics all sealed in the inner space formed by the pair of substrates and the spacer, and the inner space in the display device is hermetically sealed up.
In a display device that contains two types of particles serving as a display element, the chargeability of the particles is influenced by the ambient humidity. Concretely, the particles are over-charged in a low-humidity atmosphere, but are charged insufficiently in a high-humidity atmosphere. In addition, when the humidity inside the space sandwiched between the substrates increases, the particle-to-particle cohesiveness and the particle-to-substrate adhesiveness increase, and, as a result, the particles could hardly move when an electric field is applied thereto.
In the display device of the invention, however, since the inner space formed by the pair of substrates and the spacer is hermetically sealed up, the electric characteristics of the particles sealed in the inner space are not influenced by the ambient humidity. Therefore, the display device all the time ensures constant image formation.